Yet in the early going, the former vice president seems wary of his position as the favorite to win the 2020 Democratic presidential nomination and cognizant of an ailment that's beleaguered once promising White House hopefuls of past years: Frontrunner Flameout.

“This is a marathon,” Biden told supporters at a campaign fundraiser in Los Angeles last week. “I know all that polling stuff looks good, but it is a marathon and we have a long way to go.”

Former Vice President and Democratic candidate for United States President, Joe Biden (R) talks with a voter at The Works in Concord, New Hampshire, on Tuesday. Biden is on a two day campaign tour of New Hampshire, the first since his announcing his 2020 campaign.(Photo: CJ GUNTHER, EPA-EFE)

History shows that the former vice president is prudent not to put too much stock into his exalted position in the very early going of the crowded 2020 presidential race.

Back in late May 2015, Donald Trump was sitting in eighth place in the crowded Republican contest, according to a Quinnipiac poll. Former Florida Gov. Jeb Bush, neurosurgeon Ben Carson, former Arkansas Gov. Mike Huckabee, U.S. Sen. Marco Rubio of Florida and Wisconsin Gov. Scott Walker were among those polling ahead of him.

At the time, 21% of Republicans said there was “no way” they’d support Trump. The poll showed that Democrat Hillary Clinton would beat him 50% to 32% if Trump emerged as the GOP nominee.

In June 2007, Clinton had a 11-percentage point lead over the upstart Sen. Barack Obama, and her fellow New Yorker Rudy Giuliani was leading the GOP field, according to a national Gallup poll.

Sen. John Kerry, a Massachusetts Democrat and presidential candidate, works the crowd August 13, 2003, after his speech at the Des Moines Register Political Soapbox at the State Fair.(Photo: Register file photo)

Connecticut Sen. Joe Lieberman was atop the pack of Democratic hopefuls in June 2003, with 20% of Democrats supporting Lieberman for their party's 2004 presidential nomination. Fifteen percent supported Missouri Rep. Dick Gephardt, while 13% supported the eventual nominee, Massachusetts Sen. John Kerry, according to Gallup.

“Uneasy lies the head that wears the crown,” said Christopher Borick, director of the Muhlenberg College Institute of Public Opinion. “Everybody is targeting you. Everybody is focusing on you. You take more hits when you’re in front. Do you want to be ahead right now if you’re Joe Biden? I’d say yes, but you also don’t want to be approaching it as an impregnable place to sit, because the record says it’s not.”

Staying above the Democratic fray

Since announcing his candidacy last month, Biden has steered clear of jousting with rival Democrats and kept his aim squarely on Trump on the campaign trail.

The strategy of punching at Trump, and only Trump, has come even as fellow Democrats continue to jab at Biden.

Sen. Elizabeth Warren has hit Biden for being “on the side of the credit card companies” for his backing of the 2005 Bankruptcy Abuse Prevention and Consumer Protection Act, legislation that tightened rules on who could qualify for bankruptcy protection.

Sen. Bernie Sanders, who is running second to Biden in most major polls, has tried to poke holes into Biden’s pitch to voters that he’s a champion of the middle class by highlighting Biden’s support for NAFTA and Permanent Normal Trade Relations with China during his time in the Senate.

More recently, Biden has faced criticism from progressive groups as well as 2020 hopefuls, including Sanders and Washington Gov. Jay Inslee, after an adviser to his campaign told Reuters that Biden would seek a “middle ground” approach to combating climate change. Biden has yet to detail what his climate policy will look like.

Sen. Bernie Sanders, I-Vt. addresses The Road to the Green New Deal Tour final event at Howard University in Washington, Monday, May 13, 2019.(Photo: Cliff Owen, AP)

“The Obama-Biden Administration made historic progress on climate change, from record investment in renewable energy, to Clean Car Standards to the Paris Agreement,” Inslee said. “But the times and science have changed. We cannot simply go back to the past; we need a bold climate plan for our future.”

Biden pushed back against suggestions he’s not sufficiently committed to the issue, one that is particularly resonating with the younger electorate. He spoke specifically during a campaign stop in New Hampshire about criticism from Rep. Alexandria Ocasio-Cortez, who called a "middle ground" approach on climate change a "dealbreaker."

"You never heard me say 'middle of the road.' I’ve never been middle of the road on the environment," Biden told reporters. "Tell her to check the statements that I made and look at my record. She'll find that nobody has been more consistent about taking on the environment and the green revolution than I have."

Electability factor helps, hurts Biden

At the core of Biden’s message is that he offers the Democrat’s the best chance to beat Trump and take back the White House.

That message appeals to older and moderate voters – who will make up a large part of the electorate in early caucuses and primary states – and may be enough to help Biden buck the recent trend of early frontrunners fizzling, said Susan MacManus, a political scientist at the University of South Florida. She said Biden also benefits from the large field fracturing the support of more liberal Democratic voters.

But MacManus said that the moderate appeal that could propel Biden to his party's nomination may also prove to be his Achilles heel in the general election, when young voter enthusiasm will be essential for Democrats hopes of taking the White House. Voters ages 18 to 23 are projected to make up 1 in 10 eligible voters in 2020.

“We’re going to see how deep the generation divide is in the country,” MacManus said. “Younger people care less about the idea of electability than sticking to principles and supporting someone who shares their values and goals and aspirations. I doubt a lot of the younger people are looking at candidates and saying, ‘Can he (or she) beat Trump?’”

Borick, the Muhlenberg College pollster, counters that electability is Biden’s greatest asset and the universal desire among those on the left to beat Trump suggests that even the most liberal voters will come around to Biden for the general election.

“I don’t think we’ve seen in previous polling a party more driven by unseating the incumbent president than we do now,” Borick said.

Will Biden counterpunch Democrats?

For his part, Biden has tried to stake a position above the Democratic fray, repeatedly promising to refrain from speaking ill of his 21 major Democratic Party rivals. But as the campaign unfolds, it will undoubtedly become more difficult to ignore incoming fire from rivals.

Democrats are scheduled to hold their first debate of the election cycle next month in Miami, where his Democratic rivals will seek to contrast themselves with the frontrunner.

The legislation will give Sanders an opportunity to draw another distinction between him and Biden if they end up on the same debate stage. (Because of the unwieldy number of candidates vying for the Democratic nomination, the debates are scheduled to be split over two nights and Biden and Sanders aren’t guaranteed to appear together.)

The youngest candidate in the race, South Bend, Indiana, Mayor Pete Buttigieg, has repeatedly made the case that the country needs generational change, because the politics of the moment will decide how the next 30 or 40 years will go.

Buttigieg, 37, has frequently reminded voters that he’s 35 years junior to Trump, and likely be alive to see the impact of the big policy decisions. Left unsaid by Buttigieg is that both Biden, 76, and Sanders, 77, are even older than Trump.

Biden has said he wants to assure voters that he’s not too old to serve as president, and has already urged Americans to watch his vigor on the campaign trail.

Campaigning in Somersworth, N.H. Monday, Biden offered a folksy aside about Satchel Paige, the famous pitcher who made his Major League Baseball debut at the ripe age of 42 after the league began integrating, to downplay the importance of age.

Biden recalled a memorable exchange between Paige and reporters who were marveling after Paige became the oldest pitcher to record a win in big league history at the age of 47 – a record that was later broken.

“'Boys, I don't look at age that way.” said Biden, paraphrasing the back-and-forth between Paige and the reporters. “I look at it this way, 'How old would you be if you didn't know how old you were?' "

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New York Mayor Bill de Blasio said on May 16, 2019, he will seek the 2020 Democratic presidential nomination. De Blasio becomes the 23rd prospective Democratic challenger to President Donald Trump. "Donald Trump must be stopped. I am Bill de Blasio and I am running for president because it's time we put the working people first," he said in a video announcing his candidacy. Seen here, de Blasio speaks inside Trump Tower on May 12, 2019 about the Green New Deal demanding more energy-efficient buildings, including Trump Tower, in New York. DON EMMERT, AFP/Getty Images

Montana Gov. Steve Bullock speaks at the Des Moines Register Soapbox during a visit to the Iowa State Fair in Des Moines, Iowa on Aug. 16, 2018. Bullock on May 14, 2019 joined the growing list of candidates in the 2020 presidential race, saying he was the only Democrat who won in a red state that President Donald Trump took by 20 points in 2016. Charlie Neibergall, AP

U.S. Senator Michael Bennet, D-Colo., speaks before Senator Bernie Sanders during a rally with young voters on the campus of the University of Colorado in Boulder, Colo. Bennet says he is seeking the Democratic nomination for president in 2020. The three-term senator made the announcement May 2, 2019 on “CBS This Morning.” David Zalubowski, AP

Former Vice President Joe Biden delivers remarks at the International Brotherhood of Electrical Workers Construction and Maintenance Conference at the Washington Hilton in Washington D.C. April 5, 2019. Biden announced April 25, 2019 in a Youtube video making him one of 20 Democrats vying to become the party's 2020 presidential nominee. Jack Gruber, USAT

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